The objective of channel coding is to fight against various noises and interferences in a transmission process. Usually, the system can be endowed with an ability to automatically correct an error by manually adding redundant information, thereby ensuring the reliability of digital transmission. A Turbo code is one of the optimal Forward Error Correction (FEC) codes accepted at present, and is widely adopted in many standard protocols as a channel coding solution for data service transmission. Moreover, with the increase of decoding iterations, the decoding error-correcting performance will be continuously perfected. The Turbo codes commonly used at present include binary Turbo codes and dual-binary tail-biting Turbo codes.
Rate matching processing is a very key technology after channel coding. The objective thereof is to repeat or puncture, under the control of an algorithm, codeword bits subjected to channel coding, so as to ensure that data bit lengths after rate matching are matched with allocated physical channel resources. At present, there are mainly two rate matching algorithms: a 3rd Generation Partnership Project (3GPP) R6 rate matching algorithm and a Circular Buffer Rate Matching (CBRM) algorithm. Herein, the CBRM algorithm is a simple algorithm capable of generating an excellent pattern puncturing performance, and this rate matching algorithm is adopted in a majority of communication systems such as 3GPP2 series standards, IEEE802.16e standards and 3GPP Long-Term Evolution (LTE).
In the CBRM algorithm, under the condition that the code rate is ⅓, codeword bits output by Turbo coding will be separated into three data bit streams through separation of bits: a system bit stream, a first check bit stream and a second check bit stream. The above-mentioned data bit streams are re-arranged respectively by using a block interleaver, this processing process usually being called as intra-block interleaving. Then, in an output buffer, re-arranged system bits are put at a starting position, and thereafter, two re-arranged check bit streams are placed in a staggered manner, called as inter-block interleaving.
Moreover, in this processing process, Ndata coding bits may be selected as output of CBRM according to a desired output code rate. CBRM reads out Ndata coding bits from a certain specified starting position from the output buffer, called as bit selection. In general, the selected bits for transmission may be read out from any position in the buffer. After the last bit of a circular buffer area is read, the next bit data is the first bit position data of the circular buffer area. So, the rate matching based on circular buffer (puncture or repetition) may be implemented by using a simple method. Circular buffer also has the advantages of flexibility and granularity as for a Hybrid Automatic Repeat Request (HARQ) operation to be described below.
An HARQ is an important link adaptation technology in a digital communication system. This technology functionally refers to that: a receiving end decodes an HARQ data packet received thereby, feeds an ACK signal back to a sending end if decoding corrects, and informs the sending end to send a new HARQ data packet; and the receiving end feeds an NACK signal back to the sending end if decoding fails, and requests the sending end to re-send an HARQ data packet. The receiving end performs Incremental Redundancy (IR) or Chase combined decoding on data packets repeated for many times, so the decoding success probability may be improved, and the requirement of high reliability on link transmission is met.
Under an HARQ mode, different positions may be specified in a circular buffer to serve as read starting positions of an HARQ data packet transmitted at each time. A definition of a Redundancy Version (RV) determines a plurality of read starting positions of the HARQ data packet in the circular buffer, and the value of the RV will determine specific read starting positions of the HARQ data packet transmitted at this time in the circular buffer.
For example, in LTE, the RV defines a starting point of the circular buffer for selecting a segment of codewords to generate a current HARQ packet. If there are four RVs, four positions are evenly marked in the circular buffer from left to right in correspondence to the RVs 0, 1, 2 and 3. More specific descriptions may refer to proposals and standards for virtual CBRM of LTE, which will not be elaborated herein.
During data transmission on a network or a communication channel, data is divided into data packets for transmission. In order to improve the reliability of data transmission, an error-correcting mechanism usually needs to be provided by using a network protocol or coding. For example, during the data transmission on the internet, it is necessary to reliably transmit the data by using an error check retransmission mechanism provided by a Transmission Control Protocol (TCP). That is, when loss of data packets is detected, a sender is informed of resending. In a communication system, a Media Access Control (MAC) layer supports an ARQ mechanism, and if the data packets are wrongly transmitted, this mechanism also ensures reliable transmission by repeatedly sending the data packets.
During data transmission in a multimedia broadcast channel, because a one-way channel is used and data is sent by using a one-to-many broadcast/multicast mode, the receiving end is not allowed to feed back data packet loss and error information to the sending end, and the above-mentioned error check retransmission mechanism cannot be used. Under this condition, the data packet needs to perform Forward Error Correction (FEC) coding before sending, and in this case, a raptor code is mainly used.
The inventor of the present disclosure discovers that a prior communication system has the following problems.
As for a future HARQ-supporting communication system (e.g., a fifth mobile communication system), main scenarios and demands of 5G include Device-to-Device (D2D) communication, internet-of-things communication (MCP), Ultra-Dense Network (UDN) communication, Mobile Network (MN) communication, and ultra-reliable (UN) communication. In order to meet new 5G demands, a future 5G link enhancement technology needs to satisfy low-delay and high-throughput characteristics, so how to reduce a repeat count or repeat delay of an HARQ for a future communication system supporting the HARQ is a problem to be solved.
As for a future communication system not supporting the HARQ (e.g., future Wireless Local Area Network (WLAN) system), a target Block Error Ratio (BLER) of a physical layer data packet cannot be too low and is required to be 10−1, at least. If a data packet needs to be decomposed into a great number of coded blocks, the error rate of each coded block (BCER) is often high in requirement, and when the number N of code blocks is large (e.g., N is greater than or equal to 10), if the target BLER of the physical layer data packet is less than 0.5, the BLER is about equal to N*BCER. Hence, in order to achieve the target BLER, a low coded block target BCER is needed, and the system needs to give a great signal to noise ratio. Particularly, the system efficiency will be obviously limited under poorer channel conditions. So, how to reduce the target BCER of each coded block for the future communication system not supporting the HARQ is a problem to be solved.
An existing broadcast and multicast communication system (e.g., a DVB system and a 3GPP Multimedia Broadcast Multicast System (MBMS)) introduces a Raptor code or a Fountain code, and this erasure code is mainly applied to a long code instead of an optimal code, and as long as the code length is greatest, the code has the performance approaching the performance of the optimal code. Under the condition that the number of data packets is small (e.g., less than 200), how to design an effective performance-optimal and complexity-minimum coding solution is a problem to be solved.
In addition, packaging coding may be considered to be used during multi-path (including multi-cell and multi-RAT) flexible transmission of borne data. Under the condition that the number of data packets is small (e.g., less than 100), how to design an effective performance-optimal and complexity-minimum coding solution is a problem to be solved.
In conclusion, a communication system in the related art lacks a coding solution for a physical layer big data block (Transmission Block (TB)) which may be segmented into a great number of coded blocks.